1. Field of the Invention
The present invention relates to an imaging device and a focusing control method.
2. Description of the Related Art
In recent years, according to the increase in resolution of an imaging element such as a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor, demand for information devices having an imaging function, such as a digital still camera, a digital video camera, a mobile phone such as a smart phone, or a personal digital assistant (PDA) has rapidly increased. Such an information device having an imaging function is referred to as an imaging device.
In such an imaging device, as a focusing control method for focusing on a main subject, a phase difference auto-focus (AF) method (for example, see JP2006-133515A, JP2012-103285A, JP2011-242652A, and WO2013/047160A) is employed.
In a solid-state imaging element mounted on an imaging device that performs a focusing control based on the phase difference AF method, for example, a configuration in which pairs of phase difference detection pixels in which light shielding film openings are eccentric in opposite directions are discretely arranged on an entire imaging surface is used.
Such a phase difference detection pixel has a low sensitivity compared with that of a normal imaging pixel in which a light shielding film opening is not eccentric with respect to a photoelectric conversion unit. Thus, in normal imaging, it is necessary to interpolate detection signals of phase difference detection pixels using detection signals of imaging pixels. Accordingly, if the number of phase difference detection pixels increases, the quality of a captured image deteriorates. On the other hand, if the number of phase difference detection pixels arranged in a direction where a phase difference is detected decreases, it is not possible to enhance the accuracy of detection of the phase difference according to subjects.
JP2006-133515A, JP2012-103285A, and JP2011-242652A disclose a method for connecting detection signals of phase difference detection pixels in plural rows arranged in a direction orthogonal to a phase difference detection direction to decrease a sampling interval of signals in the phase difference detection direction, in a dedicated distance measurement sensor.
WO2013/047160A discloses a method, in an imaging device comprising an imaging element that includes imaging pixels and phase difference detection pixels, for connecting detection signals of phase difference detection pixels which are arranged at different positions in a phase difference detection direction, in different rows, to decrease a sampling interval of signals in the phase difference detection direction.